This invention relates to an electric bell of the type which is driven by a motor and adapted for use in a fire bell, an alarm bell or the like, and more particularly to a gong striking mechanism driven by a motor to strike a gong.
In a conventional electric bell as shown in FIG. 1, a pivoting plate 2 is fixed to a motor shaft. A counter-weight 3 is attached at one end of plate 2 A striking hammer 4 is attached to the other end of plate 2 and is arranged in a slot 5 to move forwardly and backwardly against a gong 6 during the rotation of a motor 7. The location of the striking hammer 4 varies each time it strikes the gong 6 so that the weight balance between the two ends of the pivoting plate 2 with respect to the rotary shaft 1 of the motor 7 can not attain an appropriate condition and fluctuates during the hammer striking motion.
Moreover, when the motor 7 starts to rotate and the striking hammer 4 strikes the gong 6 the relatively long plate 2, having at one end the counter-weight 3 and the striking hammer 4 at the other end causes the motor shaft 1 either to bend, due to the large torque imparted thereon, or to move gradually away from the shaft 1 due to the absence of a provision for fixing the shaft 1 to the plate 2. The latter case is seen when the shaft is relatively small in diameter and is insusceptible for a fixing means such as a pin to be inserted in the shaft to fix the shaft 1 and the plate 2. Therefore, the bell of the type described is disadvantageous since the rotation of the motor 7 is not smooth and is apt to fluctuate. Further, the shaft 1 is subjected to a bending force which causes irreparable damages thereto.
In order to overcome the above disadvantage, a bell as shown in FIG. 2 has been proposed employing a cam 8 fixedly attached to an axis 9 of a motor 10 and a crank rod 11 which engages the cam so as to convert the rotational motion of the motor 10 to a reciprocal motion, thereby causing a spring plate 12 to reciprocate in order to strike a gong 13 with a hammer 14 fixedly attached to the plate 12. The spring plate 12 is fixed at one end thereof to a supporting plate 15 and is connected at the other end thereof to the crank rod 11.
In the bell as described above, however, some problems exist, such as the requirement of a plurality of assembly processes, expensive cost, and difficulty in adjusting the bell to get an optimum sound volume.
Accordingly, it is an object of this invention to provide a novel gong striking mechanism in which all of the above-described drawbacks accompanying a conventional gong striking mechanism are overcome. Another object of the invention is to provide a gong striking mechanism employing reliable and simple elements to eliminate difficulties in manufacturing the bell and adjusting the bell sound volume.
With the above and other objects in view, the invention provides a gong striking mechanism comprising a driving electric motor, mounted on a frame within a gong, and a conversion means rotationally connected directly or indirectly to the motor shaft for converting continuous rotational motion of the motor shaft to reciprocal motion of a hammer, and a resilient means adapted to absorb impact strength during gong striking motion, the resilient means being disposed between the motor shaft and the hammer. Preferably the conversion means comprises a cylindrical end cam rotatably attached to the motor shaft, and a cylindrical cam follower having one end which abuts the end surface of the cam and a second end secured to a first end of a rod. The rod being capable of reciprocating movement and having a hammer fixedly connected to a second end thereof to strike the gong. A resilient means is composed of a spring which is fixed at one end thereof to the cam follower to absorb impact force during gong striking motion. Further, it may be possible to substitute the cylindrical cam follower and the reciprocal rod for a single reciprocal rod which serves both to follow the end cam and to strike the gong, such that the single reciprocal rod abuts at one end to the end cam and at the other end abuts to and strikes the hammer. Still further the gong striking mechanism in accordance with a invention preferably comprises the resilient means which is composed of a flexible tube. One end of the flexible tube is fixedly connected to the motor shaft and the other end is connected to an eccentric came. The eccentric cam being adapted to serve as said conversion means to strike the gong. The conversion means may preferably be composed of an eccentric cam rotatably fixed to the motor shaft, the cam being disposed to engage the resilient means which includes a spring plate and a hammer.
The novel features which are considered characteristic of the invention are set forth in the appended claims. This invention itself, however, as well as other objects and advantages thereof will be best understood by reference to the following detailed description of illustrative embodiments, when read in conjunction with the accompanying drawings.